An experimental drug being clinically studied for its effects on body weight in obese and overweight people has led to record-breaking weight loss for study participants — similar to surgical options, the company behind the drug suggests.
Developed by the American pharmaceutical company Eli Lilly and Company (Lilly), Tirzepatide is a weekly injection that promotes weight loss by mimicking the effects of natural hormones called incretins. These hormones lower blood sugar levels after we eat, in addition to regulating metabolic processes related to digestion.
In the case of tirzepatide, which is not yet available on the market pending further clinical research, the drug is a synthetic combination of two specific incretins, GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic). polypeptide). †
The former hormone, GLP-1, forms the basis of the anti-diabetes drug semaglutide, which was approved in the US in 2021 as a weight-loss drug. This is the first time the FDA has introduced a new weight loss treatment in several years.
That approval was given on the basis of results described as a “game-changer” for weight loss, but it appears that the formulation of tirzepatide — thanks to the addition of GIP alongside GLP-1 — could change the game again.
In Phase 3 results of the ongoing SURMOUNT-1 clinical trial investigating the effects of tirzepatide, researchers enrolled 2,539 participants who were overweight or obese (with one weight-related comorbidity but without type 2 diabetes).
The participants were given tirzepatide or a placebo over the course of 72 weeks, along with support to follow a low-calorie diet and increase their physical activity.
Tirzepatide was given at one of three different doses (either 5, 10 or 15 milligrams in the weekly injection), but all three groups saw significant levels of weight loss over the course of the study.
At the highest dose (15 mg), participants saw an average weight reduction of 22.5 percent from their body weight (24 kg or 52 lb), while the 10 mg dose resulted in 21.4 percent weight loss (22 kg or 49 lb) and 5 mg saw a 16 percent reduction in body weight (16 kg or 35 lb).
In comparison, the placebo group lost only 2.4 percent of their body weight (2 kg or 5 lb). Previously, the semaglutide weight loss studies averaged about 17 percent weight loss.
“Tirzepatide is the first investigational drug to average greater than 20 percent weight loss in a Phase 3 trial,” said clinical study physician Jeff Emmick, vice president of product development at Lilly.
While the results have not yet been peer-reviewed, Lilly says they will be submitted for such consideration in the future. Meanwhile, research in the SURMOUNT-1 study is ongoing, in addition to the related SURMOUNT studies, the results of which are expected to be announced in 2023.
However, we already know that tirzepatide disagrees with everyone who takes it. While the average weight loss results appear to outperform treatment with semaglutide, and roughly equal the weight loss patients would expect from bariatric surgery, some participants in the tirzepatide arm experienced side effects.
Depending on the dose, up to a third of the group taking tirzepatide experienced nausea, while diarrhea was also relatively common (for 18.7-23 percent of the participants). Some people also experienced vomiting and constipation, although it’s worth noting that only a small percentage of the participants dropped out of the study because of these effects.
Yet another potential barrier to taking tirzepatide is the issue of price — assuming subsequent trial results convince the FDA to approve the drug for weight loss patients. (The drug has already been submitted for regulatory review for diabetes treatment.)
As others have noted, semaglutide — sold as a weight-loss drug under the brand name Wegovy by the Danish pharmaceutical company Novo Nordisk — sells for over US$1,300 a month, and very few patients can afford such an expensive drug, especially when Medicines like this are rarely reimbursed by health insurance.
If tirzepatide follows a similar pricing strategy – on its expected but unassured future release – this could be another case of a potentially brilliant, life-changing drug that many people sadly can’t afford to buy.
“The drugs themselves seem great, but Wegovy is expensive, and the others probably will be,” neuroscientist and obesity researcher Stephan Guyenet told Gizmodo.
“This is especially true in the US, where Wegovy costs about four times more than in other countries. So the main question becomes one of access.”
Economics aside, the impressive results of these drugs nevertheless suggest that we may soon be transforming the treatment of obesity — a complex and damaging epidemic that has resisted our control for decades.
If we can deliver on that promise and ensure equal access to this new generation of obesity drugs, we can improve the health of millions of people around the world, researchers say.
“This is extremely exciting, although preliminary data show weight loss at the bariatric surgery level of a drug, one that likely offers a host of other metabolic benefits,” Scott Kahan, the director of the National Center for Weight and Wellness in Washington, D.C. , to Healio .
“Continued development of tirzepatide and similar agents could revolutionize the treatment of obesity, similar to how cholesterol and heart disease management was transformed by the advent of statin medications and how HIV management was transformed by antiretroviral drugs.”